Hydraulic brake apparatus for a vehicle

Abstract

The present invention is directed to a hydraulic brake apparatus, which includes wheel brake cylinders, and a master cylinder for advancing a master piston in response to operation of a brake pedal. A power chamber is formed behind the master piston. A reaction piston is disposed, with the front end thereof exposed in the power chamber, so as to transmit a reaction force produced by the pressure in the power chamber to the brake pedal. A power source is provided for pressurizing brake fluid stored in a reservoir to supply power pressure to the power chamber. A solenoid valve is provided for opening and closing a return passage which connects the power chamber to the reservoir, thereby to return the brake fluid thereto. A detection device is provided for detecting the amount of operation of the brake pedal. The solenoid valve is controlled in response to the amount of operation detected by the detection device to reduce the amount of the brake fluid in the power chamber. As a result, even if the brake pedal is operated during the automatic pressurization, with the power pressure supplied by the power source, the brake fluid in the power chamber is reduced by controlling the solenoid valve to be opened and closed, to obtain a sufficient stroke of the brake pedal, so that an adequate brake feeling can be obtained.

What is claimed is:  
     
       1. A hydraulic brake apparatus for a vehicle comprising: 
       wheel brake cylinders operatively mounted on wheels of said vehicle, respectively;  
       a master cylinder for advancing a master piston in response to operation of a brake pedal to supply hydraulic braking pressure to said wheel brake cylinders;  
       a power chamber formed behind said master piston;  
       a reaction piston with the front end thereof exposed in said power chamber for transmitting a reaction force produced by the pressure in said power chamber to said brake pedal;  
       a reservoir for storing brake fluid;  
       a power source for pressurizing the brake fluid stored in said reservoir to supply power pressure to said power chamber;  
       a return passage for connecting said power chamber to said reservoir to return the brake fluid thereto;  
       valve means for opening and closing said return passage;  
       detection means for detecting the amount of operation of said brake pedal; and  
       control means for controlling said valve means to be opened and closed in response to the amount of operation of said brake pedal detected by said detection means to reduce the amount of the brake fluid in said power chamber.  
     
     
       2. A hydraulic brake apparatus as set forth in  claim 1 , wherein said control means controls said valve means to increase the amount of brake fluid returned from said power chamber to said reservoir through said return passage, in response to increase of the amount of operation of said brake pedal detected by said detection means. 
     
     
       3. A hydraulic brake apparatus as set forth in  claim 2 , wherein said control means controls said valve means to control the amount of brake fluid returned from said power chamber to said reservoir through said return passage to be smaller than the amount of brake fluid discharged from said master cylinder in response to operation of said brake pedal. 
     
     
       4. A hydraulic brake apparatus as set forth in  claim 2 , wherein said valve means includes a linear solenoid valve for opening and closing said return passage, and wherein said control means controls said linear solenoid valve to be opened or closed in response to the amount of operation of said brake pedal detected by said detection means. 
     
     
       5. A hydraulic brake apparatus as set forth in  claim 1 , further comprising: 
       a regulator for regulating the power pressure discharged from said power source to produce a regulated pressure;  
       a regulated pressure chamber formed behind said reaction piston, and connected to said regulator for receiving the regulated pressure discharged therefrom; and  
       a normally closed solenoid valve disposed between said power chamber and said power source, wherein said valve means includes a normally open solenoid valve disposed between said power chamber and said reservoir, and wherein said control means controls said normally closed solenoid valve to be opened when said brake pedal is operated, and said control means controls said normally open solenoid valve to be opened and closed in response to the amount of operation of said brake pedal detected by said detection means to reduce the amount of the brake fluid in said power chamber.  
     
     
       6. A hydraulic brake apparatus as set forth in  claim 5 , wherein said control means controls said normally open solenoid valve to be opened and closed, to increase the amount of brake fluid returned from said power chamber to said reservoir through said return passage, in response to increase of the amount of operation of said brake pedal detected by said detection means. 
     
     
       7. A hydraulic brake apparatus as set forth in  claim 1 , wherein said power source includes a hydraulic pressure pump for pressurizing the brake fluid stored in said reservoir to discharge the power pressure, and an electric motor for actuating said pump. 
     
     
       8. A hydraulic brake apparatus as set forth in  claim 1 , wherein said detection means includes a sensor for detecting the hydraulic braking pressure output from said master cylinder, and a sensor for detecting a stroke of said brake pedal, and wherein said detection means detects the amount of operation of said brake pedal in response to at least one of the outputs from said sensors.